This invention is generally directed to developer compositions, and more specifically, the present invention relates to developer compositions with conductive coated carrier particles which may be prepared by dry powder processes. In embodiments of the present invention, the carrier particles are comprised of a hard magnetic core, that is, a core which when exposed to a magnetic field acquires a magnetic moment which is retained by the core after the magnetic field is removed, and which core includes, for example, strontium ferrite, and the like, with a polymeric mixture coating thereover, and more specifically, a mixture of two polymers, and dispersed in one polymer conductive components, such as carbon black, and dispersed in the second polymer a copper iodide, especially cuprous iodide, thereby enabling carriers with excellent high conductivity ranges of from about 10.sup.-10 to about 10.sup.-7 ohm/cm, and a large tribo range of from about a minus (-) 30 to a plus 30 microcoulombs per gram. The carrier particles prepared in accordance with the processes of the present invention contain in one of the polymer carrier coatings cuprous iodide in certain important amounts and certain coating weights to enable in combination with the polymer/conductive coating a certain carrier conductivity range, and a wide carrier triboelectric range, and wherein the carriers generated can be selected for a number of different xerographic copies and printers wherein carriers with certain specific conductivity and certain tribo charge are required. The carrier particles of the present invention contain important amounts, or levels of polymer coating containing additives, such as cuprous iodide, relative to the carrier core of from about 5 percent by weight to about 30 percent by weight. The weight percent of the polymeric carrier coatings is calculated, for example, by subtracting the weight of the carrier core from the total weight of all of the components of the carrier and dividing the resulting value by the total weight of all of the components of the carrier, and multiplying the result by 100. For example, when the carrier comprises 95 grams of strontium ferrite core and 2.5 grams of a polymer of 20 percent CuI/80 percent polyurethane and 2.5 grams of a polymer of 19 percent carbon black/81 percent polymethylmethacrylate, the calculated percent polymers, or coating weight in the carrier is 5 percent. In another example, when the carrier comprises 75 grams of strontium ferrite core and 20 grams of a polymer of 80 percent CuI/20 percent polyurethane and 5 grams of a polymer of 19 percent carbon black/81 percent polymethylmethacrylate, the calculated percent polymer in the carrier is {((75+20+5)-75)/100}*100=25 percent. Of importance with respect to the present invention in embodiments is the coating weight, that is the total weight percent of polymer mixture, for example first and second polymer with copper iodide, of from about 5 to about 25, about 5.5 to about 24, or about 6 to about 20 percent, or weight percent, to enable a suitable carrier triboelectric charging value range, high triboelectric charging values for the carrier, and acceptable conductivities.
Developer compositions comprised of the carrier particles illustrated herein and prepared, for example, by a dry coating process are useful in electrostatographic or electrophotographic imaging systems, especially xerographic imaging and printing processes, and digital processes, reference the Xerox Corporation 220 and 230 machines, especially xerographic processes in which the magnetic brush is highly agitated by virtue of (1) the carrier particles possessing a permanent magnetic moment, and (2) the brush composed of these particles experiencing a rapidly varying magnetic field. These xerographic development systems can function either with the magnetic brush in contact with a second member of the development system, such as the photoreceptor, an intermediate donor roll, or with the magnetic brush out of contact with the second member, for example when a non-interactive development system is desired. Additionally, the invention developer compositions comprised of substantially conductive carrier particles are useful in imaging methods wherein relatively constant conductivity parameters are desired. Furthermore, in the aforementioned imaging processes the triboelectric charge on the carrier particles can be preselected depending on the polymer composition and dispersant component applied to the carrier core, the conductive component selected, the amount of cuprous iodide selected, and the coating weight. Also, in embodiments the carrier core can contain a first continuous polymer coating, such as polymethacrylate, or a thermosetting polymer, such as a polyester/polyurethane mixture, and dispersed therein conductive components, such as conductive carbon blacks or metal oxides, in amounts, for example, of from about 1 to about 70, and preferably from about 10 to about 60 weight percent, and a second polymer with cuprous iodide contained therein in an amount of, for example, from about 75 to about 95 weight percent.